Boost Dropping
#1
I drive a 90 TII that is COMPLETELY stock.. except for a RB catback exhaust. I can drive it for ~10 minutes and it boosts great to 8.6psi like it should, but after a little bit, it drops back down to 5.5psi. As I understand it, the stock EBC is supposed to raise it to the 8.6psi. What could be causing it not to go up properly?
Note: New plugs, fuel filter, voltage to fuel pump is perfect, clean oil.
Note: New plugs, fuel filter, voltage to fuel pump is perfect, clean oil.
#4
Originally Posted by sureshot' date='Feb 24 2005, 05:32 AM
Maybe IC heat soak?
To test, after boost falls off, spray some cold water on the IC & do another run.
To test, after boost falls off, spray some cold water on the IC & do another run.
#5
I haven't checked the EBC yet, but i went out yesterday in subfreezing weather with my car. It stopped boosting up to 8.6psi and i pulled over and drizzled snow on the TMIC... lots of dry snow. Some melted but the IC wasn't even hot to the touch. After that, it still wouldn't boost past 5.5psi.
I noticed my stock boost gauge reads low (doesn't zero when the car is in the on position). IIRC, that's controlled by the pressure sensor. Maybe that thing is acting up? Maybe it's the EBC? What else should I test?
I noticed my stock boost gauge reads low (doesn't zero when the car is in the on position). IIRC, that's controlled by the pressure sensor. Maybe that thing is acting up? Maybe it's the EBC? What else should I test?
#8
Originally Posted by JackoliciousLegs' date='Mar 3 2005, 11:31 AM
I have an aftermarket gauge... don't worry. I just know that the stock boost gauge is controlled by the pressure sensor. I figured if that's screwing up, it could also be screwing other stuff up...
I have seen my stock boost gauge work, work with low readings, & fail at various times.
All along the S-AFC's signal from the pressure sensor was perfect according to the mechanical boost gauge.
The problem seems to be between the dash gauge & the ECU.
The signal to the ECU has never been a problem.
#9
Ok, just did a couple checks.
1. Stock EBC
I checked the resistance as per the FSM, and it's a solid 32 ohms... perfect
2. Pressure Sensor
5V to terminal w/ pressure sensor removed
2V read with no vacuum applied. on terminal D
0V with vacuum applied on terminal D
FSM says it should be reading 2V at 2psi vacuum. It read that w/o vacuum and read 0 with vacuum applied. Could this be the cause of my 5.5psi problem?
1. Stock EBC
I checked the resistance as per the FSM, and it's a solid 32 ohms... perfect
2. Pressure Sensor
5V to terminal w/ pressure sensor removed
2V read with no vacuum applied. on terminal D
0V with vacuum applied on terminal D
FSM says it should be reading 2V at 2psi vacuum. It read that w/o vacuum and read 0 with vacuum applied. Could this be the cause of my 5.5psi problem?
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neil_jdmr
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